1. Field of the Invention
This invention relates to the general field of coated abrasives and particularly to the type of such abrasives which have exceptionally flexible backings and which can readily be torn by hand to yield a reasonably straight torn edge. The invention also relates to the field of stitch bonded fabrics, which are a major component of the backings of the coated abrasives of the invention.
2. Description of the Prior Art
Before 1974, almost all coated abrasive cloth products were coated on woven cotton cloth, and it was common knowledge among manufacturers and users of coated abrasives that such products could usually be torn carefully by hand in such a way as to produce a substantially straight and unpuckered edge. This property of straight tear is particularly advantageous to users who can not always forecast in advance just what width of coated abrasive they will need at any given time and therefore prefer to buy relatively wide rolls of coated abrasive cloth and tear it to width as needed. While straight tearing capability along lines parallel to the machine direction of the cloth is most common, some products also will tear straight in the cross direction. These are particularly convenient to those who use coated abrasives without the aid of mechanical driving devices and often want to sand workpieces with small concave radii of curvature or small dimensions generally.
The introduction of polyester cloth for coated abrasive backings contributed to improved ruggedness and life for coated abrasives in demanding applications, but militated against straight tear. Many coated abrasives on polyester cloth, which have gained great commercial importance, are too strong for most users to tear by hand at all, and when tearing is possible, it usually does not produce straight and unpuckered edges.
Coated abrasives having arrays of straight and parallel yarns, most often of synthetic multifilament polyester, as their principal backing strength members have more recently gained commercial use. Coated abrasives of this type are described extensively in pending application Ser. No. 06/420,466 filed Sept. 29, 1982. Some stitch bonded fabrics suited to reinforce coated abrasive backings are described in pending application Ser. No. 06/664,446 filed Oct. 23, 1984. Both these applications are assigned to the assignee of the instant application.
These pending commonly assigned applications describe primarily coated abrasives which are very rugged and suited to applications in which mechanical damage to the abrasives and their backings is likely. Such coated abrasives have only limited flexibility and are difficult to use in sanding sharply contoured surfaces. Furthermore, the specific coated abrasives described in examples in these applications were almost all too strong for most potential users to tear easily by hand. If tearing was possible, a straight edge was a rare result.
Resistance to tearing is obviously one component of damage resistance, but there are many applications for coated abrasives in which mechanical damage is fairly unlikely and the convenience of tearing the coated abrasives by hand to yield straight edges is prized by users of the products. Because polyester and other synthetic yarns have other advantages over cotton in addition to superior damage resistance, and because stitch bonded fabrics have considerable cost and other advantages over woven fabrics, it is an object of the present invention to provide coated abrasives, and fabrics therefor, having the advantages of stitch bonding, synthetic yarns, facile conformability to workpieces of almost any shape, and the ability to be torn straight by hand.